Comparison of a Resonant Mirror Biosensor (IAsys) and a Quartz Crystal Microbalance (QCM) for the Study on Interaction between Paeoniae Radix 801 and Endothelin-1.

A resonant mirror biosensor, IAsys, and a quartz crystal microbalance (QCM) are known independently as surface sensitive analytical devices capable of label-free and in situ bioassays. In this study, an IAsys and a QCM are employed for a new study on the action mechanism of Paeoniae Radix 801 (P. radix 801) by detecting the specific interaction between P. radix 801 and endothelin-1 (ET-1). In the experiments, ET-1 was immobilized on the surfaces of the IAsys cuvette and the QCM substrate by surface modification techniques, and then P. radix 801 solution was contacted to the cuvette and the substrate, separately. Then, the binding and interaction process between P. radix 801 and ET-1 was monitored by IAsys and QCM, respectively. The experimental results showed that P. radix 801 binds ET-1 specifically. The IAsys and QCM response curves to the ET-1 immobilization and P. radix 801 binding are similar in reaction process, but different in binding profiles, reflecting different resonation principles. Although both IAsys and QCM could detect the interaction of P. radix 801 and ET-1 with high reproducibility and reliability through optimization of the ET-1 coating, the reproducibility and reliability obtained by IAsys are better than those obtained by QCM, since the QCM frequency is more sensitive to temperature fluctuations, atmospheric changes and mechanical disturbances. However, IAsys and QCM are generally potent and reliable tools to study the interaction of P. radix 801 and ET-1, and can conclusively be applied to the action mechanism of P. radix 801.

Amperometric choline biosensors prepared by layer-by-layer deposition of choline oxidase on the Prussian blue-modified platinum electrode.

An amperometric choline biosensor was developed by immobilizing choline oxidase (ChOx) in a layer-by-layer (LBL) multilayer film on a platinum (Pt) electrode modified with Prussian blue (PB). 6-O-Ethoxytrimethylammoniochitosan chloride (EACC) was used to prepare the ChOx LBL films. The choline biosensor was used at 0.0V versus Ag/AgCl to detect choline and exhibited good characteristics such as relative low detection limit (5x10(-7)M), short response time (within 10s), high sensitivity (88.6muAmM(-1)cm(-2)) and a good selectivity. The results were explained based on the ultrathin nature of the LBL films and the low operating potential that could be due to the efficient catalytic reduction of H(2)O(2) by PB. In addition, the effects of pH, temperature and applied potential on the amperometric response of choline biosensor were evaluated. The apparent Michaelis-Menten constant was found to be (0.083+/-0.001)x10(-3)M. The biosensor showed excellent long-term storage stability, which originates from a strong adsorption of ChOx in the EACC multilayer film. When the present choline biosensor was applied to the analysis of phosphatidylcholine in serum samples, the measurement values agreed satisfactorily with those by a hospital method.

Asymmetric electrochemical lactonization of diols on a chiral 1-azaspiro[5.5]undecane N-oxyl radical mediator-modified graphite felt electrode.

A graphite felt electrode modified with (6S,7R,10R)-4-amino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]undecane N-oxyl was prepared for electrocatalytic oxidation of diols; electrolysis of diols on the modified electrode yielded optically active lactones (92.0-96.4%), with an enantiopurity of 82-99% ee.